Why would I want to wire a pneumatic switch pair in a two-way configuration?

[robinbanks]

I bought a couple of pneumatic switches for a corridor and my plan is to just wire them so that all the commons are on the same wire (which is permanently live) and all the "normally open" contacts are on the same wire, going to the load. You can then push any switch the light will turn on, you can push any other switches in the corridor and the lights will remain on.
The lights will extinguish when the last switch has popped out and returned to its resting position, so it's a way of extending the timer if you need to spend extra time opening the front door after you've travelled down the stairs; just push the switch next to the front door and the lights will stay on longer even if the switch upstairs popped back out. This seems like the most sensible logical way that you would wire these things.

The manual for the switch also describes a seemingly standard two way wiring scenario where the permanent live comes into the common of one switch. The two switches have their "normally open" of one switch wired to the "normally closed" of the other and vice versa, and then the load is wired to the common of the other switch.

I just don't understand why you'd wire this at all, because it means you can push one switch, the light will come on. you push the other switch and the light will go off. when the first switch pops out the light will come back on, when the second switch pops out the light will go off again. What was the point of this? If anything this seems dangerous in the communal sense because you could be travelling down the stairs, and push a switch halfway down the stairs, deactivating the lights until the top one's popped out. This potentially leaves you to navigate the stairs in darkness because there's literally nothing you can do other than wait until the timer of the oldest switch expires

 

[endecotp]

Are they generic instructions, not specific to the pneumatic switch?

(Does the pneumatic switch even have a third contact?)

 

[flameport]

Instructions copied from some other switch instructions.
Or it's AI generated slop.
Or both.

 

[endecotp]

I found this one, which is not what you are describing…

( https://www.free-instruction-manuals.com/pdf/pa_359418.pdf )

I think that gives you “normal” behaviour. What’s the advantage? What do they mean by “live and switched live are at different positions”?

 

[JohnW2]

I found this one, which is not what you are describing…
( https://www.free-instruction-manuals.com/pdf/pa_359418.pdf )
I think that gives you “normal” behaviour. What’s the advantage?

What do they mean by “live and switched live are at different positions”?

I presume that it means that the 'live' (from supply) goes first to the left-hand switch, whereas the 'switched live' (to the load) comes from the right-hand one (which may be physically a long way from the left-hand one) - i.e. similar ('topographically') to the 'traditional' method of 2-way switch, as apposed to the 'modern' ('conversion') method, in which both supply and feed to load can be connected 'to' the same switch.

 

[robinbanks]

I found this one, which is not what you are describing…

( https://www.free-instruction-manuals.com/pdf/pa_359418.pdf )

View attachment 400796


I think that gives you “normal” behaviour. What’s the advantage? What do they mean by “live and switched live are at different positions”?

I think that's the same manual, as it does have that exact diagram in (Elkay 400A)

But interestingly, I found the manual:

https://www.tlc-direct.co.uk/Technical/DataSheets/Elkay/EK400A_Instructions.pdf

And the diagram I complain of is absent in that one, but present in this one:

https://www.tlc-direct.co.uk/Technical/DataSheets/Elkay/EK400Ax.pdf

The manual I have looks like the first link, but with the 2way diagram from the second link in the blank space

Perhaps I have the interim manual, somewhere between the second link (early) and first link (latest) where the manufacturer hadn't yet realised it's a nonsense

 

[SUNRAY]

AFAIC Diagram 3 is a load of tish and a pointless thing to do. Failure of the right hand switch (I find these have a higher failure rate than standard switches) could prevent the whole system working but Diagram 2 (the only normal way AFAIC) doesn't.

And this?

Can anyone think of a sensible reason?


"EDIT: Ah yes that reminds me I recall the flat my son lived for a while: Push the button at the bottom of the stairwell - lights on, push at the top - lights off, 10 minutes later the lights would come on again when no one pushed the buttons. BUT the problem? pushing again during the 10 minutes meant no lights available so a pointles way to wire them.